1. Technical Field
Example embodiments relate to a thin film transistor structure having an organic semiconductor layer.
2. Description of the Related Art
Increased interest has been generated regarding organic semiconductors since polyacetylene, as a conjugated organic polymer, was shown to exhibit semiconductor characteristics. As a result, organic semiconductors have been researched for a wide variety of applications (e.g., functional electronic devices and optical devices) because of their relative ease of molding into fibers and films, improved flexibility, relatively high conductivity, and/or relatively low production costs. Organic thin film transistors have especially been the subject of intense research.
An organic thin film transistor (OTFT) may comprise a substrate, a gate electrode, a gate insulating layer, source/drain electrodes, and an organic semiconductor layer. Organic thin film transistors may be classified as bottom contact (BC) organic thin film transistors, wherein an organic semiconductor layer is provided on source/drain electrodes; top contact (TC) organic thin film transistors, wherein source/drain electrodes are provided on an organic semiconductor layer (e.g., by mask deposition); or top gate (TG) organic thin film transistors, wherein a gate electrode is provided on a gate insulating layer.
The semiconductor layers of organic thin film transistors may be formed by printing processes at ambient pressure, unlike the semiconductor layers of silicon thin film transistors which may involve conventional silicon processes, including plasma-enhanced chemical vapor deposition (PECVD). Additionally, the overall fabrication procedure may be achieved by relatively economical roll-to-roll processes using plastic substrates. Accordingly, organic thin film transistors may be useful for various applications, including driving devices for active displays and plastic chips for smart cards and inventory tags.
However, organic thin film transistors may have a relatively high contact resistance (MΩ range) between the semiconductor layer and source/drain electrodes when compared to silicon thin film transistors. As a result, the relatively high contact resistance may render the injection of carriers ineffective, thus resulting in relatively low charge carrier mobility, relatively high driving voltage, and relatively high threshold voltage for the organic thin film transistors.